Dedicated private telephone lines between two parties have been established in the past by physically installing and maintaining a hard-wired telephone line connection between the parties. Facilities that are "manual ring down" requires the user to push a designated button on the telephone to ring the user on the other end of the hard-wired telephone line. The parties using a dedicated hard-wired telephone line with the "automatic ring down" feature may ring the other end of the line and establish a connection by simply raising the telephone handset or otherwise going "off-hook." Since the need to memorize and dial telephone numbers or even speed-dial numbers is obviated, the path of communication is established immediately. The private line service is typically favored by customers who make large volumes of calls from and to fixed locations and whose business requires continuous and uninterrupted lines of communication between those locations. A prime example of such a customer is a brokerage firm maintaining offices in Chicago and New York.
Needless to say, such dedicated hard-wired facilities are extremely expensive and difficult to install and maintain. Nevertheless, since such dedicated line service is demanded by certain telephone service subscribers, it has become desirable to provide a service that emulates a dedicated private telephone line but that does not require a physical hard-wire telephone connection. Accordingly, it has become desirable to use the existing telephone switching networks to establish private telephone line service. In particular, it is advantageous to use the rapid call setup ability of industry standard Signaling System 7 (SS7) to quickly establish private line calls with automatic ring down using the switched network.